Non-aqueous secondary batteries (non-aqueous electrolysis solution-containing secondary batteries), such as lithium ion secondary batteries, have characteristics such as compact size, light weight, high energy-density, and the ability to be repeatedly charged and discharged, and are used in a wide variety of applications. Consequently, in recent years, studies have been made to improve battery members such as electrodes for the purpose of achieving even higher non-aqueous secondary battery performance.
A positive electrode for a non-aqueous secondary battery generally includes a current collector and an electrode mixed material layer (positive electrode mixed material layer) formed on the current collector. The positive electrode mixed material layer is formed using, for example, a slurry composition that contains a positive electrode active material, a binder-containing binder composition, and so forth dispersed in a dispersion medium.
In order to further improve the performance of non-aqueous secondary batteries, attempts have been made in recent years to improve binder compositions used in positive electrode mixed material layer formation.
In one specific example, PTL 1 proposes a binder composition for a non-aqueous secondary battery positive electrode that can improve life characteristics of a non-aqueous secondary battery. The proposed binder composition contains a binder that is a hydrogenated polymer obtained through hydrogenation of a polymer including a conjugated diene monomer unit and a nitrile group-containing monomer unit, wherein the amount of platinum group elements, such as palladium, contained in the binder composition is no greater than 8×10−4 parts by mass per 100 parts by mass of the hydrogenated polymer.
In another example, PTL 2 proposes a technique for inhibiting aggregation of a polymer contained in a binder composition as a binder and improving life characteristics of a non-aqueous secondary battery by limiting the content of particulate metal components (for example, Fe, Ni, Cr, and the like) in the binder composition to no greater than 10 mass ppm.